Between December 2010 and April 2012, intensive care unit (ICU) patients in our hospital were infrequently colonized with extended-spectrum beta-lactamase-positive bacteria (ESBLs). We hypothesized that these ESBLs originated from patients' room sinks, and this was prospectively investigated by weekly culturing of patients and sinks during a 20-week period. ESBLs were isolated from all 13 sinks. Four patients became colonized with ESBLs that were genetically identical to ESBLs that had previously been isolated from the sink. One of these patients died of pneumonia caused by the ESBL. Transmission from sinks to patients was stopped by integrating self-disinfecting siphons to all sinks on the ICU. (C) 2014 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.